The invention relates to an electromagnetic shield for a room or for a building.
Known electromagnetic shields are intended to block electromagnetic waves, which are typically used for wireless radio communication, from buildings or parts of buildings, and on the other hand they are used to assure that electromagnetic radiation from a room or from a building does not get outside. Typically, they are not suited to protect technical installations like nuclear power plants from a nuclear electromagnetic pulse (NEMP) or from another electromagnetic pulse with high amplitude (HEMP—high altitude electro magnetic pulse). Such an electromagnetic pulse typically occurs when a nuclear chain reaction is set off in the air, e.g. when an atomic or hydrogen bomb is exploded at ground level, but also through targeted punctual generation (HPM—high power microwave). The electromagnetic radiation generated thereby is strong enough to disturb or destroy all electronic circuits in a large surrounding area through the induction of high currents in the circuits. In order to protect important technical installations or critical process controls, as are typically found in nuclear power plants, against failure, e.g. due to an electromagnetic nuclear pulse, no practical electromagnetic shields are known to accomplish this. The problem occurs in particular, when, for example, existing nuclear power plants have to be retrofitted with such electromagnetic shields.
From German Patent DE 37 81 272 T2 it is known to electromagnetically shield a building by covering the side walls with plates with metal grids inside, wherein the grids of neighboring plates are electrically connected and grounded. The shield described therein, however, is not suitable at all to dampen the nuclear electromagnetic pulse (NEMP) of a nuclear chain reaction sufficiently for the electronic components inside the shield to survive without being damaged. This, however, is not the goal and purpose of the shield described therein. Its purpose is to shield against electromagnetic radiation, as is typically generated by radio signals, from the inside out and from the outside in.
From German published patent application DE 196 48 544 A1 a shield against electromagnetic radiation is known, comprising a multitude of overlapping, electrically conductive and electrically connected mesh, grid, or foil sections. These sections are overlapping, and there is no electric insulation in the overlapping area, where they are glued together to establish an electrical connection. The glue joints have proven to be problematic, since it is generally not possible to assure the required, well conducting electrical connection over the whole length of the overlapping sections. Where there is no connection, or an insufficient connection of the sections, the efficiency of the shield is more or less restricted and thereby insufficient.